Question: $\dfrac{9}{8} - \dfrac{7}{10} = {?}$
Solution: $ = {\dfrac{9 \times 5}{8 \times 5}} - {\dfrac{7 \times 4}{10 \times 4}} $ $ = {\dfrac{45}{40}} - {\dfrac{28}{40}} $ $ = \dfrac{{45} - {28}}{40} $ $ = \dfrac{17}{40}$